Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The readOnlyHint annotation already signals a safe read operation. The description adds useful behavioral context: it explains that mail sent to the returned address generates events of type email.received, which goes beyond the annotation. It does not disclose potential errors or side effects, but given the annotation and the simplicity, it adds meaningful context.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two sentences, front-loads the core concept (every app is an email inbox), and delivers the return value without excess. No wasted words; every clause adds value.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple read-only tool with two optional parameters and no output schema, the description covers the essential purpose, the return value (address and webhook URL), and the relationship to events. It does not detail exact response format, but that is likely not critical. The tool is adequately described for an agent to call it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% for both parameters (app and api_key), so the schema already documents them well. The description adds the email pattern ({user}.{app}@anyhook.net) which helps understand the app parameter's role, but it does not significantly expand on the schema descriptions. Baseline of 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose: 'Returns the address and webhook URL for one of your apps.' It also explains the email inbox concept and how incoming mail becomes events, which distinguishes it from siblings like anyhook_events (which reads events) and anyhook_apps_list (which lists apps). The verb 'returns' is specific and the resource is well-defined.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage: you need this address to send email that becomes events, and it points to anyhook_events for reading them. However, it does not explicitly state when to use this tool versus alternatives, nor does it give exclusions or a direct 'use this when...' condition. The context is there but not explicit.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.